(1) FIELD OF THE INVENTION:
The invention pertains to a packer assembly for use in a subterranean well.
(2) BRIEF DESCRIPTION OF THE PRIOR ART:
Subsequent to the drilling of a subterranean oil or gas well, a string of tubular conduit commonly referred to as "casing" is run into the well. Thereafter, the casing is cemented into place. After the cementing operation, it is necessary to perforate the well so that production fluids within the production zone may flow from the production zone, through holes perforated through the cement behind the casing, into holes in the casing, and through the well bore to the top of the well.
For many years the desirability of utilizing a subterranean wellbore having a non-vertical or horizontal portion traversing a production formation has been known and appreciated in the art. Laterally directed bores are drilled radially, usually horizontally from the primary vertical wellbore, in order to increase contact with the production formation.
Most production formations have a substantial horizontal portion and, when conventional vertical wellbores are employed to tap such production formations, a large number of vertical bores must be employed. With the drilling of a wellbore having a non-vertical or horizontal portion traversing the production formation, a much greater area of the production formation may be traversed by the wellbore and the total field of drilling costs may be substantially decreased. Additionally, after a particular horizontal wellbore has produced all of the economically available hydrocarbons, the same vertical wellbore may be re-drilled to establish another horizontal portion extending in another direction and thus prolong the utility of the vertical portion of the well and increase the productivity of the well to include the total production formation.
By use of and reference to the phrase "wellbore" herein, it is intended to include both cased and uncased wells. When uncased wells are completed, the bore hole wall defines the maximum hole diameter at a given location. When cased wells are completed, the "wall" of the well will be the internal diameter of the casing conduit.
By use of the phrase "deviated well" and "deviated wellbore", it is meant to refer to wells and wellbores which comprise a vertical entry section communicating through a relatively short radius curvature portion with a non-vertical or horizontal portion communicating with the production formation. In most instances, the production formation extends for a substantial horizontal extent and the generally linear wellbore portion traverses a substantial horizontal extent of the production formation, at least up to a distance of 1000 to 2000 feet, or more. The radius portion of the wellbore has a curvature of at least 10.degree. per 100 feet of length, and preferably a curvature lying in the range of 10.degree. to 30.degree. per 100 feet of length.
In U.S. Pat. No. 3,101,783, entitled "Well Packer", issued Aug. 27, 1963, there is shown and disclosed a single grip retrievable casing packer which is manipulable between run-in and set positions by longitudinal manipulation of the tubular workstring. A similar device is disclosed in U.S. Pat. No. 3,112,795, entitled "Retrievable Subsurface Well Tool", issued Dec. 3, 1963, and discloses a patentable variation of the '783 device and includes what is commonly referred to as a "hold-down buttons" which temporarily secure the packer to the casing upon variation in tubing/casing pressure, such as when tools either above or below the packer are being activated from one position to another position, and it is desired to temporarily secure the packer in position, or to act as a securing "boost" against movement of the packer in one longitudinal direction either prior to or during setting along the inner wall of the casing. While each of these patented designs can be considered advancements in the art, neither is adapted to be activated from the running position to the set position in only one diameter of casing. In other words, these and similar tools could be inadvertently set at a depth somewhat above the desired setting depth in the subterranean well. Additionally, such packers can require rotational movement of the tubular workstring to either set or retrieve the packers, and such rotational movement is difficult in deviated wells associated with horizontal completion techniques. Accordingly, in such completion techniques, it will become difficult, if not almost impossible, to apply sufficient torque at the top of the well to manipulate the tubular workstring when it has been run in such a well through the deviated section and curved portion of the well to the horizontal section adjacent the production zone. In such instances, it would be desirable to provide a retrievable packer which is manipulable from run-in to set and retrieved position only by longitudinal manipulation, i.e., push/pull of the workstring.
In such horizontal completions, as well as many other types of completions, it is not infrequent that a "liner" of smaller diameter casing is run into the larger casing size and hung therefrom such that an expanded telescopic configuration of the casing occurs. In such instances, the retrievable packer apparatus must not be inadvertently activated in the larger diameter casing such that it is placed in the "set" position prematurely.
In one aspect of the present invention, a retrievable packer is provided having particular utility for use in horizontal completion operations, with the packer being manipulated between run-in, set and retrieving positions only by longitudinal movement of the workstring.
Another aspect of the present invention is the provision of a packer assembly which is retained in the run-in position and prevented from inadvertent manipulation to the set position until such time as the device parallels a known size of casing, or other conduit, through which it is disposed.